The regulatory role of interferon in the activity of human NK cells will be studied. We have demonstrated that human NK cells are able to synthesize and release interferon when brought in contact with tumor target cells. The produced interferon amplifies the cytotoxic response by recruiting inactive "pre-NK" cells into full cytolytic activity. In addition to this direct amplification of the cytotoxicity, interferon also inhibits suppressor cells of the human NK cell activity and this pathway may be important in certain situations where NK activity is induced. These interacting regulatory mechanisms will be studied with the aid of cell separation techniques, direct anti-interferon immunofluorescence and monoclonal anti-NK-antibodies combined with functional assays of NK activity, interferon production and suppressor cell mediated inhibition assays. We are also continuing our efforts to characterize in further detail human glioma-specific antigens. We approach the problem by producing monoclonal antibodies against the glia-specific components identified.